Presently, electrical devices known as ground fault circuit interrupters (GFCIs) enjoy widespread use in many countries around the world, in both commercial and residential environments. In fact, in many places their use is mandatory in certain locations of residential homes such as in kitchens, baths and near pools (i.e., locations close to sources of water).
A typical GFCI incorporating a duplex receptacle provides protection for devices plugged into itself and all devices located downstream of the GFCI device. Typically GFCIs are four terminal devices, two phase or AC leads for connection to AC electrical power and two LOAD leads for connection to downstream devices. Properly wired, a GFCI provides ground fault protection to downstream devices connected to its LOAD leads and to devices plugged into the GFCI receptacle itself However, if the GFCI is reverse wired or improperly wired then downstream devices are still protected if there is a ground fault but the duplex receptacle on the GFCI is not.
A perspective view illustration of a typical prior art GFCI device 12 which incorporates a duplex receptacle within its housing is shown in FIG. 1. The GFCI device 12 comprises a housing 14, two receptacles 16, 18 each comprising hot 70, 74, neutral 72, 76 and ground 77, 79 slots or contacts. Line side hot and neutral screw terminals 24 provide electrical connection points to an alternating current (AC) source. Load side hot and neutral terminals 26 provide electrical connection points for electrical devices located electrically downstream from the GFCI device 12. Tabs 28 provide means for mounting the GFCI device 12 into a wall box. A ground screw terminal 27 is provided to facilitate connecting the GFCI device 12 to a ground wire. In addition, a TEST button 20 is used to periodically test the GFCI device 12 to insure its proper functioning. A RESET button 22 is provided to reset the GFCI device 12 after it has tripped such as after testing.
A high level schematic diagram illustrating the major components of the prior art GFCI device 12 shown in FIG. 1 as properly wired to an AC electrical source is shown in FIG. 2. The AC source 17 is electrically coupled to the hot (i.e., phase) and neutral line side screw terminals 24. Electrically connected across the phase and neutral lines is the GFCI circuit 11. GFCI circuits are well known in the art. Electrical switches 13, 15 are placed in line with the phase and neutral lines. The electrical 13, 15 switches may be electromechanical relays, semiconductor switches or other suitable controllable switching devices. Electrical switch or relay 13 is operative to open circuit the phase conductor and electrical switch or relay 15 is operative to open the neutral conductor in the event a ground fault is detected. On the load side of the relays 13, 15 are the two electrical receptacles 16, 18. The hot contacts 70, 74 are electrically coupled to the phase conductor and the neutral contacts 72, 76 are electrically coupled to the neutral conductor. Ground conductors 77, 79 are electrically coupled to the system ground. The load side phase and neutral terminals 26 provide phase and neutral lines to downstream electrical devices. A pilot light 21 shows the condition of the GFCI. Such a pilot light is shown in U.S. Pat. No. 4,412,193 issued Oct. 25, 1983. See the LED pilot light 81 in FIG. 1.
Under normal operating conditions, relays 13, 15 are closed and electrical current flows to both the receptacles 16, 18 and downstream devices. In the event of a ground fault, GFCI circuitry 11 is operative to open relays 13, 15 and prevent current from flowing to the receptacles 16, 18 and downstream electrical devices connected to the load side terminals.
However, if the GFCI 11 is miswired (miswiring is as shown in FIG. 3, when the GFCI trips (i.e., detects a ground fault) electrical current is properly prevented from flowing to downstream devices via relays 13, 15 opening but electrical power is still present at the two receptacles 16, 18. Power is present at the receptacles 16, 18 in this case because the receptacles 16, 18 are now located before the relays 13, 15 (i.e., further upstream). Thus, in the event the GFCI 11 trips, all downstream devices are protected but the GFCI's own receptacles remain live after the GFCI 11 trips.
One reason that this problem exists is that in new construction, both the input line and downstream cables appear identical when the installer is connecting a new ground fault circuit interrupter. This is especially a problem in new construction where there is no power available in order to test which cable is leading current into the device. The problem is compounded when it is considered that most GFCIs have a test button that will trip and shut off the power when pushed to verify operations of internal functions in the GFCI. However, use of the test button does not indicate whether the built in duplex receptacle is protected. Typical users may not be aware of this. Users simply test the device after installation and verify that the unit trips upon pressing the test button by way of an audible click, for example. This gives the user a false sense that all is well. What is actually happening when the GFCI 11 is reverse wired is that the GFCI 11 disconnects power from and protects everything downstream, but does not protect the receptacle contacts of the GFCI 11 itself. The device will trip depending on the condition of internal components and irrespective of how the GFCI 11 was wired. It does not matter that the GFCI 11 was reverse wired when it was tested.
If the ground fault circuit interrupter is inadvertently powered through its LOAD terminals, the GFCI 11 will still trip normally when confronted with a ground fault and all downstream receptacles will still be protected. However, due to the internal connections, the GFCI's own receptacle terminals will still remain live after the GFCI 11 trips.
Currently, all GFCI's are being shipped with an instruction label attached over the LOAD terminals as per UL requirements. The Consumer Product Safety Commission is asking for something more substantial then simply a warning label. The warning label simply informs the installer to be careful when wiring the LOAD terminals. The label covers those terminals and must be removed if the terminals are to be used. Though this gives a better chance that the warning will be read, something more likely to ensure safety is desirable.
Therefore it is apparent that there is a need for an automatic way to sense when a GFCI is miswired and to indicate to the user an improperly wired GFCI. In addition, when the GFCI is improperly reverse wired the user needs to be alerted with an indicator that cannot be turned off until the electricity is disconnected and the GFCI is correctly wired. Although the background art has attempted to solve this problems the so called solutions have their own disadvantages and drawbacks. For example, one approach utilizes a GFCI with reverse line polarity lamp indicator to indicate proper installation of the GFCI. See, for example, U.S. Pat. No. 4,412,193 issued to Bienwald et al. on Oct. 25, 1983 and assigned to the owner of the present invention. However, a push button needs to be manually pressed in accordance with instructions in order to detect whether the GFCI is miswired. An apparent drawback with this scheme is that the test is never self initiating, i.e., automatic, since the user must always remember to follow the instructions and to actually press a button to test the GFCI. U.S. Pat. No. 5,477,412 issued to Neiger et al. on Dec. 19, 1995 and owned by the assignee of the present invention, is directed to a ground fault circuit interrupter GFCI incorporating miswiring prevention circuitry. Miswiring sense circuitry automatically triggers the generation of visual and audible alarms in the event of miswiring conditions. The circuit employs an alarm inhibiting technique that incorporates sense circuitry connected to the AC terminals on one side of the internal GFCI switches or relays and alarm generation circuitry connected to the load terminal on the opposite side. The electronic scheme of the Neiger et al. patent requires additional circuitry typically in the form of an additional IC chip which significantly adds to the cost of the GFCI. A simpler and more cost-effective means of preventing miswiring is desirable. A mechanical means of automatically triggering an interrupter device upon powering the device is needed.
It is therefore an object of the present invention to provide a mechanism for indicating reverse wiring of an interrupter circuit device.
It is another object of the present invention to provide a mechanism for indicating reverse wiring of an interrupter device which is simple to use and inexpensive and easily manufactured.
Another object of the present invention is to provide a mechanism capable of automatically indicating when a GFCI is miswired or not properly electrically connected to its source of electrical power and to subsequently generate an alarm indicating to the user that a potentially unsafe condition exists.
Still another object of the present invention is to provide a reliable miswiring indicating mechanism which indicates when a GFCI is correctly connected between an AC power source and downstream electrical devices and when it is incorrectly connected in reverse between such AC power source and downstream electrical devices.
Yet another object of the present invention is to have the indicator remain in the on state once generated, until the user corrects the miswiring problem. More specifically, once the indicator turns on, it cannot be shut off without removing the device and installing the device properly.
Still yet another object of the present invention is to provide both a visual indicator and an audible indicator in the event a miswiring condition is detected. The visual indicator might be in the form of a blinking light. The audible indicator might be in the form of a buzzing or high tone sound that could beep on and off at a suitable rate.
An additional object of the invention is to provide a mechanical means to automatically trigger an interrupter device upon installation to test whether the interrupter device is reverse wired.
To that end, a mechanism for indicating reverse wiring of an interrupter device is provided hereby. These and other objects of the invention are accomplished by providing a mechanism for indicating reverse wiring of a interrupter device comprising means for automatically triggering the interrupter device when the interrupter device is first powered, and indicator means electrically connected between phase and neutral lines in the interrupter device for indicating when the interrupter is reverse wired with a load connected to line terminals of the interrupter device and a source of power connected to load terminals of the interrupter device. In one embodiment of the invention there is provided a method for indicating reverse wiring of an interrupter device.
Another embodiment of the invention provides an auxiliary device for pushing a test button of an interrupter device comprising means for securing the auxiliary device to the interrupter adjacent the test button, and a protrusion for pushing the test button when the auxiliary device is secured to the interrupter device.
A further embodiment of the invention provides an interrupter system comprising an interrupter device which comprises a sensor generating a sensor signal; sensing circuit means for detecting an undesirable condition based on said sensor signal and for generating a control sense signal when the undesirable condition is detected; switching circuit means for selectively passing current in accordance with the control sense signal; contactor means including switches located in phase and neutral lines for selectively interrupting current between a power source and a load by opening the switches when the switching circuit means passes current; receptacle means connected to the phase and neutral lines; and a test button for simulating an undesirable condition; and an auxiliary device for pushing the test button comprising means for securing the auxiliary device to the interrupter device adjacent the test button; and a protrusion for pushing the test button when the auxiliary device is secured to the interrupter device.
The invention further provides a circuit for indicating reverse wiring of an interrupter device comprising triggering means for triggering the interrupter device when the interrupter device is first powered; and indicator means electrically connected between phase and neutral lines for indicating when the interrupter device is reverse wired with a load connected to line terminals of the interrupter device and a source of power connected to load terminals of the interrupter device.
The invention also provides a method for indicating the reverse wiring of an interrupter device.